Automatic selection of stimulation chamber for ventricular resynchronization therapy

ABSTRACT

A method and apparatus for selection of one or more ventricular chambers to stimulate for ventricular resynchronization therapy. Intrinsic intracardia electrograms that include QRS complexes, are recorded from a left and right ventricle. A timing relationship between the intrinsic intracardia electrograms recorded from the left and right ventricle is then determined. In one embodiment, the timing relationship is determined using a delay between a left ventricular and a right ventricular sensed intrinsic ventricular depolarizations and a duration interval of one or more QRS complexes. In one embodiment, the duration of QRS complexes is determined from either intracardiac electrograms or from surface ECG recordings. One or more ventricular chambers in which to provide pacing pulses are then selected based on the timing relationship between intrinsic intracardia electrograms recorded from the right and left ventricle, and the duration of one or more QRS complexes.

TECHNICAL FIELD

The present invention relates to medical devices and in particular to amedical device for automatically selecting stimulation chamber, orchambers, based on sensed cardiac signals.

BACKGROUND

When functioning properly, the human heart maintains its own intrinsicrhythm, and is capable of pumping adequate blood throughout the body'scirculatory system. However, some people have irregular cardiac rhythms,referred to as cardiac arrhythmias. Such arrhythmias result indiminished blood circulation. One mode of treating cardiac arrhythmiasuses drug therapy. Drugs are often effective at restoring normal heartrhythms. However, drug therapy is not always effective for treatingarrhythmias of certain patients. For such patients, an alternative modeof treatment is needed. One such alternative mode of treatment includesthe use of a cardiac rhythm management system. Such systems are oftenimplanted in the patient and deliver therapy to the heart.

Cardiac rhythm management systems include, among other things,pacemakers, also referred to as pacers. Pacers deliver timed sequencesof low energy electrical stimuli, called pace pulses, to the heart, suchas via an intravascular leadwire or catheter (referred to as a “lead”)having one or more electrodes disposed in or about the heart. Heartcontractions are initiated in response to such pace pulses (this isreferred to as “capturing” the heart). By properly timing the deliveryof pace pulses, the heart can be induced to contract in proper rhythm,greatly improving its efficiency as a pump. Pacers are often used totreat patients with bradyarrhythmias, that is, hearts that beat tooslowly, or irregularly.

Cardiac rhythm management systems also include cardioverters ordefibrillators that are capable of delivering higher energy electricalstimuli to the heart. Defibrillators are often used to treat patientswith tachyarrhythmias, that is, hearts that beat too quickly. Suchtoo-fast heart rhythms also cause diminished blood circulation becausethe heart isn't allowed sufficient time to fill with blood beforecontracting to expel the blood. Such pumping by the heart isinefficient. A defibrillator is capable of delivering a high energyelectrical stimulus that is sometimes referred to as a defibrillationcountershock. The countershock interrupts the tachyarrhythmia, allowingthe heart to reestablish a normal rhythm for the efficient pumping ofblood. In addition to pacers, cardiac rhythm management systems alsoinclude, among other things, pacer/defibrillators that combine thefunctions of pacers and defibrillators, drug delivery devices, and anyother implantable or external systems or devices for diagnosing ortreating cardiac arrhythmias.

One problem faced by cardiac rhythm management systems is the treatmentof heart failure (also referred to as “HF”). Heart failure, which canresult from long-term hypertension, is a condition in which the musclein the walls of at least one of the right and left sides of the heartdeteriorates. By way of example, suppose the muscle in the walls of theleft side of the heart deteriorates. As a result, the left atrium andleft ventricle become enlarged, and the heart muscle displays lesscontractility. This decreases cardiac output of blood through thecirculatory system which, in turn, may result in an increased heart rateand less resting time between heartbeats. The heart consumes more energyand oxygen, and its condition typically worsens over a period of time.

A deterioration of the heart's conduction system often accompanies heartfailure. Normally, intrinsic signals of the heart's conduction systemoriginate in the sinoatrial (SA) node in the upper right atrium. Thesesignals travel through and depolarize the atrial heart tissue to triggerthe contraction of the right and left atria. The intrinsic atrial heartsignals are received by the atrioventricular (AV) node which, in turn,triggers a subsequent ventricular intrinsic heart signal that travelsthrough the specialized conduction system (Purkinje Fibers) anddepolarizes the ventricular heart tissue such that resultingcontractions of the right and left ventricles are triggeredsubstantially simultaneously.

In the above example, when the left side of the heart has becomeenlarged due to heart failure and the conduction system in the leftventricle is blocked, the ventricular intrinsic heart signals may travelthrough and depolarize the left side of the heart more slowly than inthe right side of the heart. This condition is referred to as leftbundle branch block (LBBB). As a result, the left and right ventriclesdo not contract simultaneously, but rather, the left ventricle contractsafter the right ventricle. This reduces the pumping efficiency of theheart. Moreover, in the case of LBBB, for example, different regionswithin the left ventricle may not contract together in a coordinatedfashion.

Heart failure can be treated by biventricular (or left-ventricular)coordination therapy that provides pacing pulses to both right and leftventricles. See, e.g., Mower U.S. Pat. No. 4,928,688. Heart failure mayalso result in an overly long atrioventricular (AV) delay between atrialand ventricular contractions, again reducing the pumping efficiency ofthe heart. Providing heart failure patients with improved pacing andcoordination therapies for improving AV-delay, coordinating ventricularcontractions, or otherwise increasing heart pumping efficiency continuesto be an area in which improved techniques and therapy protocols areneeded.

SUMMARY

The present subject matter provides for improved pacing and coordinationtherapies for heart failure patients. The present subject matterincludes a method and apparatus for recording intrinsic electrograms,including QRS complexes, of left and right ventricles. A timingrelationship is then determined between the intrinsic electrograms ofthe left and the right ventricles. A selection of one or moreventricular chambers in which to provide pacing pulses is then madebased on the timing relationship between intrinsic electrograms of theleft and the right ventricles.

In one embodiment, determining the timing relationship includescalculating a delay between a left ventricular and a right ventricularsensed intrinsic ventricular depolarizations and measuring a durationinterval of one or more QRS complexes. In one embodiment, intrinsicintracardiac electrograms are sensed of the left and right ventricles.The delay is determined by detecting peaks of the sensed intrinsicventricular depolarizations and calculating the delay between thedetected peaks of the intrinsic ventricular depolarizations sensed fromthe left ventricular and the right ventricles. Additionally, theduration of the QRS complexes are determined from either intracardiacelectrograms or from surface ECG recordings.

The selection of one or more ventricular chambers then includesselecting one or more ventricular chambers in which to provide pacingpulses based on the duration interval of the QRS complex and the delaybetween the left ventricular and the right ventricular sensed intrinsicventricular depolarizations. For example, in selecting one or moreventricular chambers, a suggestion to pace in a left ventricle is madewhen the duration interval of the one or more QRS complexes is greaterthan or equal to a first threshold value and the difference between theleft ventricular and the right ventricular sensed intrinsic ventriculardepolarizations is greater than a second threshold value. In oneembodiment, the first threshold value is 120 millisecond and the secondthreshold value is zero (0). Alternatively, in selecting one or moreventricular chambers, a suggestion to pace in both the left ventricleand the right ventricle is made when the duration interval of one ormore QRS complexes is greater than or equal to the first threshold valueand the difference between the left ventricular and the rightventricular sensed intrinsic ventricular depolarizations is greater thanthe second threshold value. Finally, in selecting one or moreventricular chambers, a suggestion to pace in a right ventricle when theduration interval of one or more QRS complexes is greater than or equalto the first threshold value and the difference between the leftventricular and the right ventricular sensed intrinsic ventriculardepolarizations is less than or equal to the second threshold value. Inone embodiment, this suggestion is made through the use of either animplantable pulse generator and/or a medical device programmer.

In one embodiment, the apparatus of the present subject matter includesat least one receiver, where the receiver receives intrinsic intracardiaelectrograms from the left ventricle and the right ventricle. Theseelectrograms include a left ventricular and a right ventricular sensedintrinsic ventricular depolarizations having QRS complexes. In anadditional embodiment, the receiver receives the QRS duration intervalof one or more QRS complexes measured from a surface ECG.

The apparatus further includes a controller, where the controllerdetermines a timing relationship between intrinsic electrograms recordedfrom the left and right ventricle. In one embodiment, the controllercalculates a delay between the left ventricular and the rightventricular sensed intrinsic ventricular depolarizations and is adaptedto receive a duration interval of one or more QRS complexes. In oneembodiment, the QRS duration interval is provided to the controller frommeasurements made from a surface ECG recording. In an alternativeembodiment, the controller determines the duration interval of the QRScomplexes from the sensed cardiac signals.

The apparatus further includes a ventricular chamber selector. Theventricular chamber selector selects one or more ventricular chambers inwhich to provide pacing pulses based on the timing relationship betweenintrinsic intracardia electrograms recorded from the right and leftventricle. In one embodiment, the ventricular chamber selector selectsone or more ventricular chambers in which to provide pacing pulses basedon the duration interval of the QRS complexes and the delay between theleft ventricular and the right ventricular sensed intrinsic ventriculardepolarizations, as described above. The apparatus of the presentsubject matter can be incorporated into a medical device programmerand/or an implantable pulse generator, where the implantable pulsegenerator includes a first cardiac lead and a second cardiac lead, wherethe first and second cardiac leads each include electrodes for sensingthe intrinsic intracardia electrograms from the left ventricle and theright ventricle.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is one embodiment of a method according to the present subjectmatter;

FIG. 2 is one embodiment of a method according to the present subjectmatter;

FIG. 3A shows patient data on a scatter plot of R_(LV)-R_(RV) intervals(ms) vs. Atrial to R_(LV) intervals (ms);

FIG. 3B shows patient data on a bar graph of R_(LV)-R_(RV) intervals(ms) vs. Bundle Branch Block Type;

FIG. 4 is a schematic view of a medical device programmer and animplantable medical device with leads implanted in a heart, whereportions of the heart have been removed to show detail, according to oneembodiment of the present subject matter;

FIG. 5 is a block diagram of an implantable medical device according toone embodiment of the present subject matter;

FIG. 6 is a perspective view of a medical device programmer and animplantable medical device with leads according to one embodiment of thepresent subject matter; and

FIG. 7 is a block diagram of a medical device programmer according toone embodiment of the present subject matter.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings that form a part hereof, and in which is shown byway of illustration specific embodiments in which the invention may bepracticed. These embodiments are described in sufficient detail toenable those skilled in the art to practice the invention, and it is tobe understood that the embodiments may be combined, or that otherembodiments may be utilized and that structural, logical and electricalchanges may be made without departing from the spirit and scope of thepresent invention. The following detailed description is, therefore, notto be taken in a limiting sense, and the scope of the present inventionis defined by the appended claims and their equivalents.

The present methods and apparatus will be described in applicationsinvolving implantable medical devices for treating heart failureincluding, but not limited to, implantable pulse generators such aspacemakers, cardioverter/defibrillators, pacer/defibrillators, andbiventricular or other multi-site resynchronization devices. However, itis understood that the present methods and apparatus may be employed inunimplanted devices, including, but not limited to, external pacemakers,cardioverter/defibrillators, pacer/defibrillators, biventricular orother multi-site resynchronization devices, monitors, medical deviceprogrammers and recorders.

In one embodiment, the present subject matter is implemented in animplantable pulse generator. The implantable pulse generator includescardiac leads that allow for ventricular cardiac signals to be sensedfrom left and right ventricular regions of the heart. From informationderived from the sensed cardiac signals a selection is made as to whichof either the right, left or both ventricular chambers of the heart isto be paced. In one example, relative delays between intrinsic cardiacdepolarizations of the right and left ventricles are used to determinewhich, or both, ventricular chamber is to be paced. In one embodiment,the ventricle that is activated later (as measured by a laterintracardiac lead depolarization) is selected as the stimulationchamber. Since only detection of intracardiac depolarizations areneeded, the present subject matter is useful as an automaticsite-optimization feature in a ventricular resynchronization therapydevice, such as a biventricular stimulation device.

In one embodiment, the suggestion for which ventricular chamber tostimulate (left, right or both) is based on the sensed cardiacconduction between the right and left ventricles of the heart. Differenttiming relationships between cardiac complexes in the cardiac signalssensed from the right and left ventricular regions can indicatedifferent conduction disorder types. For example, in branch bundle blocktype disorders regions of the left or right ventricle do not contracttogether in a coordinated fashion. As a result, the left and rightventricles do not contract simultaneously, but rather, the leftventricle contracts after the right ventricle or vice versa. As aresult, the pumping efficiency of the heart is reduced. To increase thepumping efficiency of the heart, identifying and selecting a ventricularpacing location, or locations, that allow for synchronized ventricularcontractions would be beneficial to patients with conduction disorderproblems. The present subject matter addresses these issues.

FIG. 1 shows one embodiment of a method 100 according to the presentsubject matter. At 110, intrinsic electrograms of the right ventricleand the left ventricle are recorded. In one embodiment, the electrogramrecordings are made from both a right ventricular location and a leftventricular location through the use of electrodes implanted withinand/or on the surface of the heart. For example, the electrograms aresensed as unipolar cardiac signals using an implantable pulse generatorcoupled to one or more cardiac leads implanted in or adjacent the rightventricle and/or left ventricle. In addition, bipolar cardiac signalsare sensed from the left and right ventricles so as to allow forventricular depolarizations to be sensed from around the distal portionsof the implanted leads.

At 120, a timing relationship is determined between intrinsicelectrograms of the left and right ventricle. In one embodiment, theelectrograms include indications of ventricular depolarizations, such asR-waves and/or QRS-complexes that are both indicators of intrinsicventricular depolarizations. In one embodiment, the timing relationshipincludes calculating a delay between the left ventricular and the rightventricular sensed intrinsic ventricular depolarizations. For example,the delay between left ventricular and the right ventricular sensedintrinsic ventricular depolarizations is taken as the difference betweena time of a first ventricular contraction in a first ventricular chamber(e.g., left ventricle or right ventricle) and a time of a secondventricular contraction in a second ventricular chamber (e.g., the rightventricle when the first chamber is the left ventricle and the leftventricle when the first chamber is the right ventricle), where the twoventricular contractions are part of the same cardiac contraction andboth contribute to one cardiac cycle of the heart.

Determining the timing relationship also includes measuring a durationinterval of one or more QRS complexes. Measuring the duration intervalof QRS complexes is accomplished in any number of ways. For example, theduration interval of the QRS complexes is measured manually from aprintout of a surface ECG measurement. Alternatively, the durationinterval of the QRS complexes is measured electronically from the sensedand recorded cardiac electrograms.

At 130, one or more ventricular chambers in which to provide pacingpulses are then selected based on the timing relationship betweenintrinsic electrograms of the right and the left ventricles. In oneembodiment, the selection at 130 is based on the duration interval ofthe QRS complex and a calculated delay between the left ventricular andthe right ventricular sensed intrinsic ventricular depolarizations.

FIG. 2 shows an additional embodiment of a method 200 according to thepresent subject matter. At 210, intrinsic intracardia electrograms ofright ventricular and left ventricular cardiac signals are recorded. Inone embodiment, the right and left ventricular cardiac signals aresensed as unipolar cardiac signals using an implantable pulse generatorcoupled to one or more cardiac leads implanted in or adjacent the rightventricle and/or left ventricle. In one embodiment, a first cardiacsignal is sensed from a right ventricular region and a second cardiacsignal is sensed from a left ventricular region. In one embodiment, thefirst cardiac signal is sensed from an apex of the right ventricle,while the second cardiac signal is sensed from a left ventricular freewall. Alternatively, the second cardiac signal is sensed from electrodesimplanted transvenously through the coronary sinus so as to position theelectrodes adjacent the left ventricle. In an additional embodiment, theelectrograms are sensed through the use of a surface 12-lead ECGmeasurement or a PRM surface ECG system.

At 220, the timing relationship is determined between intrinsic rightand left electrograms recordings. In one embodiment, a portion of thetiming relationship is determined by calculating a delay between a firstventricular chamber (e.g., left ventricle or right ventricle) and a timeof a second ventricular contraction in a second ventricular chamber(e.g., the right ventricle when the first chamber is the left ventricleand the left ventricle when the first chamber is the right ventricle),where the two ventricular contractions are part of the same cardiaccontraction and both contribute to one cardiac cycle of the heart. Forexample, cardiac depolarizations are detected in each of the right andleft cardiac signals. In one embodiment, the cardiac depolarizationsinclude R-waves, which are indications of ventricular contractions. Thetime at which the ventricular contractions occurred is then recorded,where R_(L) is designated as the time at which the depolarization in theleft ventricle occurred and R_(R) is designated as the time at which thedepolarization in the right ventricle occurred. In one embodiment, thetime the R-wave occurred is taken as the peak (i.e., the point ofmaximum deflection during depolarization) of the sensed intrinsicventricular depolarizations (e.g., the R-waves). The delay between theventricular chambers is then calculated by taking the difference betweenthe detected peaks of the intrinsic ventricular depolarizations sensedfrom the left ventricle and the right ventricle (i.e., the differencebetween R_(L) and R_(R)). The difference between R_(L) and R_(R) is thenused in determining which, or both, ventricular chamber should be paced.

The timing relationship also includes measuring a duration interval ofone or more QRS complexes. Measuring the duration interval of QRScomplexes is accomplished in any number of ways. For example, the QRScomplex duration interval is manually measured. Measuring the QRScomplex duration interval is accomplished by sensing the electrogramsusing any of the above-mentioned techniques and recording/printing thesensed cardiac signal on a paper strip chart recording at 50millimeters/second. In one embodiment, the QRS complex durationintervals are measured from cardiac signals sensed on leads II, V₁ andV₆ of a 12-lead ECG, where lead V₆ is placed at the midaxillary line, atthe same level as lead V₄. Alternatively, QRS complex duration intervalsare measured from cardiac signals sensed from leads II and V₁ of a PRMsurface ECG system, where lead V₁ is placed at the fourth intercostalspace, just to the right of the sternum. In one embodiment, the QRSduration is measured from the printout of the cardiac signal usingstandard practice for determining the start and end of the QRS complex.For example, the QRS duration is measured between a point at which theinitial deflection for the Q-wave is sensed and a point where the S-wavereturns to baseline of the cardiac signal. Alternatively, the QRSduration is measured from individual leads, where the maximum durationof the QRS interval from among the individual leads is taken as thefinal result.

At 230, one or more ventricular chambers are selected in which toprovide pacing pulses based on the timing relationship between intrinsicelectrograms recorded of the right and the left ventricles. In oneembodiment, this selection is based on the duration interval of the QRScomplexes and the time of occurrence for R_(L) and R_(R). For example,the determination as to the ventricular chamber or chambers to pace isbased on the comparison of the duration interval of the QRS complexes toan established value and the value of the difference between R_(L) andR_(R). So, when the duration interval of the QRS complexes is greaterthan or equal to a first threshold value and the difference betweenR_(L) and R_(R) (i.e., R_(L)−R_(R)) is greater than a second thresholdvalue, then the patient is likely a left bundle branch block type. Inthis situation the suggested pacing chamber would be either the leftventricle or biventricular (left ventricle and right ventricle).Alternatively, when the duration interval of the QRS complexes isgreater than or equal to the first threshold value and the differencebetween R_(L) and R_(R) (i.e., R_(L)−R_(R)) is less than or equal to thesecond threshold value, then the patient is likely a right bundle branchblock type. In this situation the suggested pacing chamber would be theright ventricle. In one embodiment, the first threshold value is set at120 milliseconds and the second threshold value is set at zero (0).

FIGS. 3A and 3B show data collected from fifty four (54) human patientsreceiving ventricular resynchronization therapy. The data indicate thatwhen QRS complexes have a duration interval greater than or equal to 120milliseconds, the decision as to whether a patient has a left bundlebranch block or a right bundle branch block can be determined by thevalue of the difference between the R_(L) and R_(R) values, aspreviously described.

As mentioned previously, the present subject matter is implemented inany number of implantable or external medical devices. These medicaldevices include, but are not limited to, implantable pulse generators,such as pacemakers and cardioverter/defibrillators,pacer/defibrillators, and biventricular or other multi-siteresynchronization devices. Other devices include, but are not limitedto, external pacemakers, cardioverter/defibrillators,pacer/defibrillators, biventricular or other multi-siteresynchronization devices, monitors, medical device programmers andrecorders.

FIG. 4 shows one embodiment of an implantable pulse generator system 400according to the present subject matter. The implantable pulse generatorsystem 400 includes biventricular pacing ability, the ability to sensecardiac signals from and provide pacing pulses to both the right andleft ventricular regions of the heart. Examples of biventricularpacemakers include U.S. Pat. Nos. 5,792,203 and 4,928,688, which arehereby incorporated by reference in their entirety.

Biventricular pulse generators have been found to be useful in treatingheart failure (HF), a clinical syndrome in which an abnormality ofcardiac function causes cardiac output to fall below a level adequate tomeet the metabolic demand of peripheral tissues. HF can be due to avariety of etiologies, with ischemic heart disease being the mostcommon. Some HF patients suffer from some degree of AV block such thattheir cardiac output can be improved by synchronizing atrial andventricular contractions with dual-chamber pacing using a shortprogrammed AV delay time. It has also been shown, however, that some HFpatients suffer from intraventricular conduction defects (a.k.a. bundlebranch blocks). The cardiac outputs of these can be increased byimproving the synchronization of right and/or left ventricularcontractions. Identifying which, or both, ventricular chamber to pace isthen important in treating these cardiac conditions.

In FIG. 4, the implantable pulse generator 400 includes a first cardiaclead 404, a second cardiac lead 408 and a third cardiac lead 412. Eachlead 404, 408 and 412 further includes an insulative lead body thatincludes insulated lead conductors that couple connector pins and/orrings at a proximal end of lead to each electrode on the lead 404, 408and 412. The implantable pulse generator 400 further includes aconnector block 416 adapted to releasable couple leads 404, 408 and 412to the pulse generator and to couple the electrodes located on the leadsto the electronic control circuitry located within the implantable pulsegenerator 400. The electronic circuitry within the implantable pulsegenerator 400 senses cardiac signals from the heart and provideselectrical pulses, such as pacing and/or defibrillation pulses, underpredetermined conditions of the heart. The electronic circuitry alsocontains transmitting and receiving circuitry for communicating with anexternal medical device programmer 417.

In the embodiment shown in FIG. 4, the first cardiac lead 404 includes afirst ventricular pacing/sensing electrode 420 positioned at or near adistal end 422 of the first cardiac lead 404. The first cardiac lead 404further includes a first defibrillation electrode 424 and a seconddefibrillation electrode 426, where the electrodes 424 and 426 arepositioned on lead 404 to allow the first pacing/sensing ventricularelectrode 420 and the first defibrillation electrode 424 to bepositioned in a right ventricle 428 and the second defibrillationelectrode 426 positioned in at least a portion of a right atrium 430and/or a portion of a major vein to the heart, such as the superior venacava 432.

Electrodes 424 and 426 allow for bipolar cardiac signals to be sensedfrom the right ventricular region, while electrode 420 allows forunipolar (near-field) cardiac signals to be sensed from the rightventricle. In addition, electrodes 420, 424 and 426 and the implantablepulse generator housing 436, in a “hot can” configuration, allow fordifferent combinations of electrodes and the housing 436 to be used insensing the cardiac signals from and for delivering electrical energypulses to at least the right ventricular region of the heart.

The second cardiac lead 408 includes a second ventricular sensing/pacingelectrode 444 and a third ventricular sensing/pacing electrode 448. Inone embodiment, the second ventricular sensing/pacing electrode 444 is afull or partial annular ring electrode positioned at or near a distalend 450 of the second cardiac lead 408. Alternatively, the secondventricular sensing/pacing electrode 444 is a distal tip electrodepositioned at the distal end of the second cardiac lead 408. The thirdventricular sensing/pacing electrode 448 is positioned on the lead 408proximal to the second electrode 444 to allow for the electrodes 444 and448 to be positioned within a coronary vein 454 and through the coronaryveins (such as the lateral or posterior vein) so that the electrodes 444and 448 are adjacent the left ventricle 458 to allow for sensingintrinsic heart signals from the left ventricle 458 and providing one ormore of resynchronization stimulations or defibrillation shocks. In oneembodiment, the second cardiac lead 408 of a size and shape adapted tobe positioned through the coronary sinus vein 454 so as to allow theelectrodes 444 and 448 to be positioned adjacent the left ventricle 458.

Electrodes 444 and 448 allow for bipolar cardiac signals to be sensedfrom and pacing pulses to be delivered to the left ventricular region ofthe heart. Alternatively, unipolar cardiac signals could be sensed andcoordinated paces shocks could be delivered between either electrode 444or 448 and the housing 436 of the implantable pulse generator.

The third cardiac lead 412 includes a first atrial sensing/pacingelectrode 460 and a second atrial sensing/pacing electrode 462, whereboth electrodes 460 and 462 are spaced apart and positioned at or near adistal end 464 of the third cardiac lead 412. In one embodiment, thefirst atrial sensing/pacing electrode 460 is used in conjunction withthe housing 436 for unipolar pacing or sensing from the right atrium430. Alternatively, the first and second electrodes 460 and 462 are usedto pace bipolarly or to sense bipolar cardiac signals between the twoelectrodes 460 and 462. Additional pacing/sensing electrodes can beincluded on the third cardiac lead 412 to allow for bipolar sensing andpacing of the right atrium 430.

The apparatus of the present subject matter is not limited to animplantable pulse generator. The apparatus of the present subject mattercan be generally considered to be implemented as an automaticsite-optimization feature in ventricular resynchronization therapy thatcan be carried out by an external apparatus (e.g., a medical deviceprogrammer or external ventricular resynchronization therapy device) oran implantable pulse generator (e.g., an implantable ventricularresynchronization therapy device such as a pacemaker and/or acardioverter/defibrillator).

FIG. 5 is a schematic drawing illustrating generally by way of example,but not by way of limitation, one embodiment of the implantable pulsegenerator 400 coupled by leads 404, 408 and 412 to the heart. In onesuch embodiment, the implantable pulse generator 400 providesbiventricular resynchronization therapy to coordinate right ventricularand left ventricular contractions, such as for heart failure patients.FIG. 5 shows one embodiment of control circuitry 500 within theimplantable pulse generator housing 436. The housing 436 is electricallyconductive and acts as a reference electrode in unipolar pacing andsensing.

In the present embodiment, the implantable pulse generator 400 isadapted to receive the first, second and third leads 404, 408 and 412,in connector block 416 and to couple electrodes 420, 424, 444, 448, 460and 462 on the cardiac leads to at least one receiver, where thereceiver receives intrinsic intracardia electrograms from a leftventricle and a right ventricle. In the present embodiment, the at leastone receiver includes cardiac signal amplifiers 504, 508 and 512 thatreceive cardiac signals from electrodes 420, 424, 444, 448, 460 and 462via contacts 514, 516, 518, 520, 522 and 523, respectively. Contact 524is provided to couple to electrode 426.

In one embodiment, any combination of bipolar and/or unipolar cardiacsignals are sensed using the electrodes 420, 424, 444, 448, 460 and 462.For example, a unipolar cardiac signal is sensed from the rightventricle between electrode 422 and the housing 436. In addition, aunipolar cardiac signal is sensed from the left ventricle betweenelectrode 444 or 448 and the housing 436. In one embodiment, QRS complexduration intervals are sensed and measured, as described above, from theunipolar cardiac signal sensed from the right ventricle and/or the leftventricle. Finally, a unipolar cardiac signal from the right atrium issensed from either the first or second atrial sensing/pacing electrode(460 or 462) and the housing 436.

In one embodiment, an output from amplifier 504 is shown coupled to aright ventricular depolarization sensor 530 to allow for a bipolarcardiac signal to be sensed from the right ventricle 428 (FIG. 4)between the first ventricular pacing/sensing electrode 420 and the firstdefibrillation electrode 424. The output from amplifier 508 is showncoupled to a left ventricular depolarization sensor 534 to allow for abipolar cardiac signal to be sensed from the left ventricle 458 (FIG. 4)between the second ventricular sensing/pacing electrode 444 and thethird ventricular sensing/pacing electrode 448. The output fromamplifier 512 is shown coupled to an atrial depolarization sensor 536 toallow for a bipolar cardiac signal to be sensed between the first andsecond atrial sensing/pacing electrodes 460 and 462.

The control circuitry 500 further includes amplifier 540 that is coupledto the first defibrillation electrode 424 and the second defibrillationelectrode 426 to allow for bipolar far-field cardiac signals to besensed from the heart. From this signal it is possible to measure theduration interval of sensed QRS complexes and to use this value aspreviously described. In an additional embodiment, the housing 436 isused as an additional electrode in common with the second defibrillationelectrode 426 to allow for the far-field cardiac signal to be sensedbetween the first defibrillation electrode 424 and the seconddefibrillation electrode 426/housing 436. The output from amplifier 540is shown coupled to a QRS-complex detector 540. In one embodiment, theQRS-complex detector 540 identifies QRS-complexes detected in thecardiac signal from amplifier 540 and supplies this information tocontroller 550 either for further processing by the controller 550 orfor being transmitted to a medical device programmer 554, as will bedescribed below.

The information from the right ventricular depolarization sensor 530 andthe left ventricular depolarization sensor 534 are then used by thecontroller 550 to determine the timing relationship between theintrinsic intracardia electrograms recorded from the left and rightventricle. In one embodiment, the controller 550 calculates a delaybetween the left ventricular and the right ventricular sensed intrinsicventricular depolarizations. In one example, the controller 550 detectspeaks of the sensed intrinsic ventricular depolarizations and calculatesthe delay between the detected peaks of the intrinsic ventriculardepolarizations sensed from the left ventricular and the rightventricles.

In addition to calculating the delay, the controller 550 also receives aduration interval of one or more QRS complexes. In one embodiment, theduration interval of the QRS complexes is calculated by the QRS-complexdetector 544. Alternatively, the duration interval is calculated fromthe paper strip chart recording of the ventricular signals, aspreviously described, and supplied to the controller 550 from themedical device programmer 554.

The control circuitry 500 further includes a ventricular chamberselector 560 coupled to the controller 550. The ventricular chamberselector 560 selects one or more ventricular chambers in which toprovide pacing pulses based on the timing relationship between intrinsicintracardia electrograms recorded from the right and left ventricle. Inone embodiment, the ventricular chamber selector 560 selects one or moreventricular chambers in which to provide pacing pulses based on theduration interval of the QRS complexes and the delay between the leftventricular and the right ventricular sensed intrinsic ventriculardepolarizations, as previously discussed. For example, the ventricularchamber selector 560 identifies a left ventricle for pacing when theduration interval of the one or more QRS complexes is greater than orequal to 120 milliseconds and the difference between the leftventricular and the right ventricular sensed intrinsic ventriculardepolarizations is greater than zero (0). Additionally, the ventricularchamber selector 560 identifies both a left ventricle and a rightventricle for pacing when the duration interval of the one or more QRScomplexes is greater than or equal to 120 milliseconds and thedifference between the left ventricular and the right ventricular sensedintrinsic ventricular depolarizations is greater than zero (0). Finally,the ventricular chamber selector 560 identifies a right ventricle forpacing when the duration interval of one or more QRS complexes isgreater than or equal to 120 milliseconds and the difference between theleft ventricular and the right ventricular sensed intrinsic ventriculardepolarizations is less than or equal to zero (0).

The controller 550 also analyzes the sensed cardiac signals to determinewhen and if to deliver electrical energy pulses to the heart. In oneembodiment, the microprocessor implements one or more analysis protocolsstored in a memory 566 to analyze one or more of the sensed cardiacsignals and to provide pacing, cardioversion and/or defibrillationtherapy to one or more chambers of the heart under certain predeterminedconditions. Memory 566 is also used to store one or more sensed cardiacsignals to be downloaded to the medical device programmer 554 foranalysis. In one embodiment, the control circuitry 500 communicates withthe medical device programmer 554 through a receiver/transmitter 570,where cardiac signals, programs and operating parameters for theprograms for the implantable medical device are transmitted and receivedthrough the use of the programmer 556 and the transmitter/receiver 570.Power for the control circuitry 500 is supplied by a battery 574.

The controller 550 further controls a pace output circuit 580 and adefibrillation output circuit 588 to provide pacing, cardioversionand/or defibrillation therapy to one or more chambers of the heart undercertain predetermined conditions. In one embodiment, the pace outputcircuit 580 is coupled to contacts 514, 516, 518, 520, 522 and thehousing 436 to allow for pacing between the electrode combinations of420 and 424, 420 and the housing 436, 444 and 448, 444 or 448 and thehousing 436, 460 and 462, and 460 and the housing 436. Thedefibrillation output circuit 588 is shown coupled to electrodes 424,426 and (optionally) housing 436 to allow for defibrillation energypulses to be delivered to a heart.

FIG. 6 shows one embodiment of a medical device programmer 554 accordingto the present subject matter. The medical device programmer 554 isadapted to be positioned outside the human body for communication withthe implantable pulse generator 400, as previously described. In oneembodiment, a communication link 608 is established between the medicaldevice programmer 554 and the implantable pulse generator 400, asdescribed above.

In one embodiment, the medical device programmer 554 includes electroniccircuitry within a housing 610, where a graphics display screen 612 isdisposed on an upper surface 614 of the housing 610. The programmer 554further includes a drive 618 for reading and writing instructions usedby the electronic circuitry of the programmer 554. The graphics displayscreen 612 is operatively coupled to the electronic circuitry within thehousing 610 and is adapted to provide a visual display of graphicsand/or data to the user.

The programmer 554 further includes input devices to the electroniccircuitry. For example, the programmer 554 includes a touch-sensitivedisplay screen, such that the user interacts with the electroniccircuitry by touching identified regions of the screen with either theirfinger or with a stylus (not shown). In addition, the programmer 554further includes an alphanumeric key board 620 for providinginformation, such as programmable values for the implantable medicaldevice 604, to the electronic circuitry and the medical device 604.

The programmer 554 further includes a programming head 624. Theprogramming head 624 is used to establish the communication link 608between the electronic circuitry within the programmer 554 and theimplantable pulse generator 400. In one embodiment, the communicationlink 608 is a radio frequency link. The telemetry link between theimplantable pulse generator 400 and the programmer 554 allows theelectronic circuitry coupled to the graphics display screen 612 to becoupled to the electronic control circuitry of the implantable pulsegenerator 400. The programming head 624 is coupled to the electroniccircuitry of the medical device programmer through cable 628. FIG. 6also shows the programmer 554 having a printer 630 which allows forcardiac signals received from the implantable pulse generator 400 anddisplayed on the graphics display screen 612 to be displayed on a paperprintout 634. Adjustments for printer speed and scale of the printedcardiac signals is adjustable through the use of the display screen 612and the electronic circuitry within the programmer 600.

FIG. 7 shows one embodiment of control circuitry 700 for the programmer554. The control circuitry 700 includes a receiver/transmitter circuit708, a ventricular chamber selector 712, a controller 716, a memory 720,a data input/output 724 and an in/out drive 730. In one embodiment, thereceiver/transmitter circuit 708 receives intrinsic intracardiaelectrograms from a left ventricle and a right ventricle. In oneembodiment, the intrinsic intracardia electrograms from the leftventricle and the right ventricle are sensed using an implantable pulsegenerator, as previously described. The controller 716 then determines atiming relationship between intrinsic intracardia electrograms recordedfrom the left and right ventricle. In one embodiment, the controller 716calculates the delay between the left ventricular and the rightventricular sensed intrinsic ventricular depolarizations. In oneembodiment, the controller 716 detects peaks of the sensed intrinsicventricular depolarizations and calculates the delay between thedetected peaks of the intrinsic ventricular depolarizations sensed fromthe left ventricular and the right ventricles, as previously described.

The controller is also adapted to receive the duration interval of oneor more QRS complexes. In one embodiment, the duration interval of theQRS complexes are measured from a print-out of the sensed electrograms,as previously described, where the electrograms are printed on printer736 under the control of controller 716 and under the directionsprovided through the data input/output 724. The QRS duration interval isthen provided through the data input/output 724 via prompts displayed onthe display screen 612 (not shown in FIG. 7) and data received via thekeyboard 620 (not shown in FIG. 7). In an additional embodiment, the QRSduration is measured from printout from a surface ECG and then manuallyentered into the control circuitry 700.

The ventricular chamber selector 712 then selects one or moreventricular chambers in which to provide pacing pulses based on thetiming relationship between intrinsic intracardia electrograms recordedfrom the right and left ventricle. In one embodiment, the timingrelationship used is based on the duration interval of the QRS complexesand the delay between the left ventricular and the right ventricularsensed intrinsic ventricular depolarizations, as previously described.The results are then displayed on the display screen 612. The user canthen elect to accept the suggested results and program the implantablemedical device with the suggested settings.

Although specific embodiments have been illustrated and describedherein, it will be appreciated by those of ordinary skill in the artthat any arrangement which is calculated to achieve the same purpose maybe substituted for the specific embodiment shown. This application isintended to cover any adaptations or variations of the presentinvention. Therefore, it is intended that this invention be limited onlyby the claims and the equivalents thereof.

We claim:
 1. An apparatus, comprising: at least one receiver, where the receiver receives QRS complexes of a left ventricle and a right ventricle; a controller, where the controller determines a timing relationship between QRS complexes of the left and right ventricle; and a ventricular chamber selector coupled to the controller, where the ventricular chamber selector selects one or more ventricular chambers in which to provide pacing pulses based on the timing relationship between QRS complexes of the right and left ventricle.
 2. The apparatus of claim 1, wherein the apparatus is incorporated into a medical device programmer.
 3. The apparatus of claim 1, wherein the apparatus is incorporated into an implantable pulse generator, where the implantable pulse generator includes a first cardiac lead and a second cardiac lead, where the first and second cardiac leads each include electrodes for sensing the QRS complexes from the left ventricle and the right ventricle.
 4. An apparatus, comprising: at least one receiver, where the receiver receives intrinsic electrograms of a left ventricle and a right ventricle; a controller, where the controller determines a timing relationship between intrinsic electrograms of the left and right ventricle; and a ventricular chamber selector coupled to the controller, where the ventricular chamber selector selects one or more ventricular chambers in which to provide pacing pulses based on the timing relationship between intrinsic electrograms of the right and left ventricle; wherein the intrinsic electrograms include a left ventricular and a right ventricular sensed intrinsic ventricular depolarizations having QRS complexes, and wherein the controller calculates a delay between the left ventricular and the right ventricular sensed intrinsic ventricular depolarizations and is adapted to receive a duration interval of one or more QRS complexes, and wherein the ventricular chamber selector selects one or more ventricular chambers in which to provide pacing pulses based on the duration interval of the QRS complexes and the delay between the left ventricular and the right ventricular sensed intrinsic ventricular depolarizations.
 5. The apparatus of claim 4, wherein the at least one receiver receives a QRS duration interval of one or more QRS complexes measured from a surface ECG.
 6. The apparatus of claim 4, wherein the ventricular chamber selector identifies a left ventricle for pacing when the duration interval of the one or more QRS complexes is greater than or equal to a first threshold value and the difference between the left ventricular and the right ventricular sensed intrinsic ventricular depolarizations is greater than a second threshold value.
 7. The apparatus of claim 6, wherein the first threshold value is 120 milliseconds and the second threshold value is zero (0).
 8. The apparatus of claim 4, wherein the ventricular chamber selector identifies both a left ventricle and a right ventricle for pacing when the duration interval of the one or more QRS complexes is greater than or equal to a first threshold value and the difference between the left ventricular and the right ventricular sensed intrinsic ventricular depolarizations is greater than a second threshold value.
 9. The apparatus of claim 8, wherein the first threshold value is 120 milliseconds and the second threshold value is zero (0).
 10. The apparatus of claim 4, wherein the ventricular chamber selector identifies a right ventricle for pacing when the duration interval of one or more QRS complexes is greater than or equal to a first threshold value and the difference between the left ventricular and the right ventricular sensed intrinsic ventricular depolarizations is less than or equal to second threshold value.
 11. The apparatus of claim 10, wherein the first threshold value is 120 milliseconds and the second threshold value is zero (0).
 12. The apparatus of claim 4, wherein the controller detects peaks of the sensed intrinsic ventricular depolarizations and calculates the delay between the detected peaks of the intrinsic ventricular depolarizations sensed from the left and the right ventricles.
 13. A method, comprising: recording QRS complexes, of a left and a right ventricle; determining a timing relationship between QRS complexes of the left and the right ventricle; and selecting one or more ventricular chambers in which to provide pacing pulses based on the timing relationship between QRS complexes of the left and the right ventricle.
 14. A method, comprising: recording intrinsic electrograms, including QRS complexes, of a left and a right ventricle; determining a timing relationship between intrinsic electrograms of the left and the right ventricle; and selecting one or more ventricular chambers in which to provide pacing pulses based on the timing relationship between intrinsic electro grams of the left and the right ventricle; where determining the timing relationship includes calculating a delay between a left ventricular and a right ventricular sensed intrinsic ventricular depolarizations and measuring a duration interval of one or more QRS complexes; and selecting one or more ventricular chambers includes selecting one or more ventricular chambers in which to provide pacing pulses based on the duration interval of the QRS complex and the delay between the left ventricular and the right ventricular sensed intrinsic ventricular depolarizations.
 15. The method of claim 14, wherein selecting one or more ventricular chambers includes suggesting pacing in a left ventricle when the duration interval of the one or more QRS complexes is greater than or equal to a first threshold value and the difference between the left ventricular and the right ventricular sensed intrinsic ventricular depolarizations is greater than a second threshold value.
 16. The method of claim 15, wherein suggesting includes setting the first threshold value at 120 milliseconds and the second threshold value at zero (0).
 17. The method of claim 14, wherein selecting one more ventricular chambers includes suggesting pacing in both the left ventricle and the right ventricle when the duration interval of one or more QRS complexes is greater than or equal to a first threshold value and the difference between the left ventricular and the right ventricular sensed intrinsic ventricular depolarizations is greater than a second threshold value.
 18. The method of claim 17, wherein suggesting includes setting the first threshold value at 120 milliseconds and the second threshold value at zero (0).
 19. The method of claim 14, wherein selecting one or more ventricular chambers includes suggesting pacing in a right ventricle when the duration interval of one or more QRS complexes is greater than or equal to a first threshold value and the difference between the left ventricular and the right ventricular sensed intrinsic ventricular depolarizations is less than or equal to a second threshold value.
 20. The method of claim 19, wherein suggesting includes setting the first threshold value at 120 milliseconds and the second threshold value at zero (0).
 21. The method of claim 14, wherein sensing intrinsic ventricular depolarizations includes sensing intrinsic ventricular depolarizations from a left ventricular free wall and an apex of a right ventricle.
 22. The method of claim 14, wherein calculating the delay includes detecting peaks of the sensed intrinsic ventricular depolarizations and calculating the delay between the detected peaks of the intrinsic ventricular depolarizations sensed from the left and the right ventricles.
 23. The method of claim 14, wherein measuring the duration interval of one or more QRS complexes includes recording a surface ECG that includes the one or more QRS complexes and measuring the duration interval of the one or more QRS complexes from the recorded surface ECG.
 24. A method, comprising: sensing intrinsic ventricular depolarizations, including QRS complexes, of a left ventricle and a right ventricle; calculating a delay between a left ventricular and a right ventricular sensed intrinsic ventricular depolarizations; measuring a duration interval of one or more QRS complexes; and selecting one or more ventricular chambers in which to provide pacing pulses based on the duration interval of the QRS complex and the delay between the left ventricular and the right ventricular sensed intrinsic ventricular depolarizations.
 25. The method of claim 24, wherein selecting one or more ventricular chambers includes suggesting pacing in a left ventricle when the duration interval of the one or more QRS complexes is greater than or equal to a first threshold value and the difference between the left ventricular and the right ventricular sensed intrinsic ventricular depolarizations is greater than a second threshold value.
 26. The method of claim 25, wherein suggesting includes setting the first threshold value at 120 milliseconds and the second threshold value at zero (0).
 27. The method of claim 24, wherein selecting one or more ventricular chambers includes suggesting pacing in both the left ventricle and the right ventricle when the duration interval of one or more QRS complexes is greater than or equal to a first threshold value and the difference between the left ventricular and the right ventricular sensed intrinsic ventricular depolarizations is greater than a second threshold value.
 28. The method of claim 27, wherein suggesting includes setting the first threshold value at 120 milliseconds and the second threshold value at zero (0).
 29. The method of claim 24, wherein selecting one or more ventricular chambers includes suggesting pacing in a right ventricle when the duration interval of one or more QRS complexes is greater than or equal to a first threshold and the difference between the left ventricular and the right ventricular sensed intrinsic ventricular depolarizations is less than or equal to a second threshold value.
 30. The method of claim 29, wherein suggesting includes setting the first threshold value at 120 milliseconds and the second threshold value at zero (0).
 31. The method of claim 24, wherein sensing intrinsic ventricular depolarizations includes sensing intrinsic ventricular depolarizations from a left ventricular free wall and an apex of a right ventricle.
 32. The method of claim 24, wherein calculating the delay includes detecting peaks of the sensed intrinsic ventricular depolarizations and calculating the delay between the detected peaks of the intrinsic ventricular depolarizations sensed from the left and the right ventricles.
 33. The method of claim 24, wherein sensing intrinsic ventricular depolarizations includes recording a surface ECG that includes one or more QRS complexes and measuring the duration interval of the one or more QRS complexes from the recorded surface ECG. 